It is already known, in particular from French patent specification No. FR 1 461 607 A, to provide a headlight which has a single light source, in this case a monofilament lamp, which co-operates with a reflector which is adapted to tilt about a horizontal axis at right angles to its optical axis. In its downwardly tilted position, the dipped beam, i.e. the beam which is intended to prevent dazzling of the occupants of oncoming vehicles, is formed. The reflector is raised in order to obtain a main beam, or cruising beam, of longer range.
This particular known type of headlight is of a construction which is completely unsuitable for modern headlights, and in particular those which further include means for correcting the orientation of the beam both in elevation and azimuth, these correcting means being either manual or automatic.
It is also known, from German patent specification DE 4 418 733 A, to provide a headlight which is adapted to produce from a single light source (such as a filament or an arc), together with a single reflector, both of these two types of beam. In this connection, the reflector has a fixed portion and one or more moveable portions. The displacement of the moveable portions, by means of appropriate actuators, effects the change from one type of beam to the other.
However, this approach is disadvantageous, in that it greatly complicates the design and manufacture of the reflector, and in some cases it gives rise to losses of light, or optical faults, especially at the interfaces between the fixed and moveable portions of the reflector.
United Kingdom patent specification No. GB 2 192 449 A discloses a headlight in which the operation of changing from the dipped beam mode to the main beam mode is effected by tilting the reflector by means of two devices, each of which acts on one respecting bearing point, or support point, of the reflector. However, that particular arrangement is expensive, because it makes use of two control devices for changing the beam from the dipped mode to the main beam mode. In addition, these two control devices are entirely dedicated to the change from dipped to main beam, and no other device for correcting the orientation of the beam (for example any dynamic correction device) is provided in that headlight.